My vehicle randomly doesn’t start. It can go for a month or so and then just doesn’t start. If I jump start it it will start and then go for a while. I just replaced the battery, what could it be?
What vehicle? Mazda 323
Any other recent work besides the battery? No
Any aftermarket items (Lights, stereo, alarm)? Aftermarket stereo
Diagnosis by phone: This could be a few different things. Starter contacts could be bad and the extra battery is creating enough power when jump starting to overcome the resistance in the bad contacts. Battery could be bad, even though it’s brand new. Alternator could be bad which leads to a dead battery and a no-start condition. I’ll have to get my hands on this one to get a final diagnosis.
Final Diagnosis: Vehicle was dropped off and died in the driveway. Had to jump start it to get it into the garage. I first checked the voltage from post to post. Battery voltage was OK but not great (12.68V). It should be enough to start the vehicle. Then I checked from the positive (+) post to the ground wire and it dropped to 12.62V. There’s a little loss, but that’s probably just the little corrosion between the post and the negative (-) cable end. Next I checked from the negative post to the positive cable and that dropped to 12.45V. Need to check that cable end a little more. Pulled the negative cable end off first, for safety sake. There was a little corrosion in there, so I cleaned it up with the brush. Pulled the positive cable end off and found a lot of corrosion on the inside of the cable end. Enough that it wouldn’t come off with the brush. Before I replace that cable end I pulled out my heavy duty jumper wires. I jumped from the positive battery post to the positive cable end (where there was no corrosion) and hooked up the existing negative cable end. It started right up. That cable end needs to be replaced. So I replaced the positive cable end and hooked up the new positive and then the existing negative cable end. Go to start and nothing. It’s still dead. OK, so what did I miss. Rechecked the battery voltage in my three different places and checked the fuse block. Looks like I’ve only got a little over 5V at the fuse block. Pulled off the negative cable end and checked the resistance between the cable end and the body ground bolt. Resistance was all over the map. Checked the resistance between the bare wire between the cable sheathing and the cable end and resistance was 00.2 ohms. This cable end needs to be replaced also. Once that cable end was replaced and hooked up the car started right up. Took the car for a quick test drive (<1 mile) to see if the battery was charging. Voltage before the test drive was 12.68V and after the test drive it was 12.90V. Looks like the battery is taking a charge now.
Solution: Replace both battery cable ends. Battery charging well now and car starts every time.